Investigators say the suspect told them he believed the mail carrier poisoned him and his family when the two used to be neighbors.By Jessica Guay

By: KDKA-TV’s Meghan Schiller, Jessica Guay, Shelley Bortz, Royce Jones and Jennifer Borrasso

COLLIER TOWNSHIP, Pa. (KDKA) — Police in Collier Township say a gunman opened fire on a postal worker as he delivered mail on Thursday morning.

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The shooting happened on Columbia Avenue near the intersection with Suburban Avenue just after 10 a.m.

(Photo Credit: KDKA)

Neighbors tell KDKA they heard multiple gunshots and saw a vehicle leaving the area. Someone called 911 and Collier Township Police arrived to find the mail carrier, identified as 58-year-old Louis Vignone of Moon Township, shot dead. Officials say he was shot multiple times, including in the head.

WATCH: KDKA’s Royce Jones reports

After the shooting, police say the suspect, identified as Eric M. Kortz, parked his van in the Carnegie Police Department’s parking lot and walked into the station.

No police were there at the time because they were all responding to the scene. The shooter allegedly told the department secretary he wanted to turn himself in. She asked him to wait until an officer got there.

According to court paperwork, Kortz told police that he shot Vignone because he thought the mail carrier and his family poisoned him and his family with cyanide when the two were neighbors.

A neighbor KDKA spoke with said she got a sense something was wrong when she moved in six years ago, but she never expected this.

“We are just thinking of Lou,” said neighbor Sheila Kirkpatrick.

(Photo Credit: KDKA)

A house on Tybee Street in Pittsburgh’s West End is where Kortz lives with his brother.

“There were never any disturbances at the house. It was quiet. He always said hello and goodbye to me,” Kirkpatrick said.

She said Vignone, his wife and kids lived behind Kortz on Tyndall Street. When Kirkpatrick moved in, she heard rumors that Kortz and Vignone did not get along.

WATCH: KDKA’s Jennifer Borrasso reports

“I did not see them interact with each other. They kept their distance,” Kirkpatrick said.

The neighbor said the Vignone family moved to Moon Township in the spring of 2018.

“His wife told me goodbye and they were starting fresh,” Kirkpatrick said.

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Another neighbor told KDKA’s Jennifer Borrasso that Kortz, a couple of months ago, said something big was going to happen and the whole city of Pittsburgh would know about it.

The court documents say Kortz told investigators he found Vignone on his mail route, then “went to put some bullets in him” before dropping his gun, getting in his van and driving to the department.

(Photo: KDKA Photojournalist Steve Willing)

“Just why? Who? I don’t know, he was just doing his job. Why?” said witness Debbie Bock.

Debbie Bock lives on Columbia Avenue with her husband Ken, just steps away from the Collier Township crime scene.

“The mail guy was one of the most loved guys in the neighborhood, everybody talks to him,” said Ken Bock. “He’s been here for as long as I can remember, and I’ve lived here 20 years.”

When Ken’s phone rang early Thursday morning, he never expected this.

“I was not home, I was working, my wife called me hysterical and said that this just happened in front of our house,” he said.

(Photo Credit: Aaron Sledge/KDKA Photojournalist)

His wife described what she heard: “I was sitting in my chair watching TV this morning and I heard the shots and kind of puzzled me because I knew it was close. I knew it wasn’t from the gun club which is up the road.”

“She knew something was wrong right away and especially after she seen the van speeding away squealing tires,” said Ken.

Debbie said she heard the shots, a vehicle’s door slam and the squealing tires of the alleged get-away van. She quickly realized someone had fatally shot the neighborhood’s mail carrier multiple times.

“He turned himself in, so I mean I guess I’m grateful for that but at that point, it’s too late. You’ve already done your damage,” said Debbie.

WATCH: KDKA’s Shelley Bortz reports

Neighbors tell KDKA’s Meghan Schiller the mail carrier had recently talked about retiring after this winter and always brought a smile to their faces.

“I saw his son here and I wanted to run to him and hug him, but I couldn’t so it’s just not fair. It’s not right. This world is sad. People don’t need to do that kind of stuff,” Debbie said.

Kortz appeared before a judge Thursday night. Because Vignone was a federal employee, the proceeding took place in federal court. Kortz faces one count of murder of a United States employee and a firearm charge.

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He’ll stay behind bars until his preliminary hearing, scheduled for Oct. 12. The crimes he’s accused of carry the possibility of life imprisonment or death.